Any clue whether it requires certain hardware support? I know it was only added with the stock firmware of the latest generation of devices…

I ran a quick test with it (from current git) on my old WRT54GSv4 last night, comparing CPU use under heavy traffic. Saturating my downlink at ~750 KB/s, with one or two active connections, I saw values like:

I am far from having done any real scientific testing, but I can at least say that the post-build-54 implementation seems solid enough (i.e. it doesn't break anything observable). It _may_ be placebo effect, but it would *seem* that things are considerably more responsive, especially VPN traffic (go figure).